The rate of removal of benzene, toluene, ethylbenzene and the xylene isomers
(BTEX) from contaminated groundwater is needed to design remediation
processes. Benzylsuccinic acid (BSA) and methyl-benzylsuccinic acid (methyl
BSA) are unambiguous metabolites of anaerobic BTEX biodegradation. An
analytical method for quantitative determination of BSA in groundwater samples
was developed. Samples containing BSA and methyl BSA were extracted onto
0.5 g of styrene-divinylbenzene, eluted with ethyl acetate, and methylated with
diazomethane. Gas chromatography coupled to mass spectrometry with electron
impact ionization was used for separation and detection. The recovery from spiked
1 L groundwater samples was 88 to 100 %. The precision of the method, indicated
by the relative standard error was ± 4% with a method detection limit of 0.2 μg/L.
The method was then used to analyze samples from single-well push-pull tests
conducted by injecting deuterated toluene and xylene into BTEX-contaminated
wells in order to demonstrate in-situ biodegradation. Unambiguous evidence for
deuterated toluene and xylene biodegradation was obtained with the observation of
deuterated BSA and methyl BSA coupled with the utilization of nitrate presumably
due to denitrification as terminal-electron-accepting process. Minimum first-order
degradation rates for deuterated toluene estimated from formation of BSA were
0.0004 to 0.001 day⁻¹. Rates of methyl BSA formation were not calculated because
methyl BSA, although detected, was not above the quantitation limit. Removal
rates of deuterated toluene and o-xylene were not directly measurable because the
rates were too low to measure significant changes in parent compound
concentrations. Wells for which the formation of deuterated BSA and methyl BSA
were observed had lower relative concentrations of toluene and xylenes relative to
total BTEX than wells for which no deuterated BSA and methyl BSA were
observed. Retardation factors for injected deuterated toluene and background
toluene of 2 and 14, respectively, were obtained from push-pull tests conducted to
determine toluene transport properties. Differences in retardation factors for
injected and background toluene indicate differences between injected and
background solute transport and is a topic that requires further study. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29505 |
| Date | 30 August 2001 |
| Creators | Reusser, Dominik E. |
| Contributors | Field, Jennifer A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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